Is Auth0 worth paying for ?

I am building a web application which requires user logins. Whats the difference in using auth0.com and using an PHP library for authorisation ? http://ift.tt/1P2vPy8

Is there any substantial gain in paying to use auth0.com rather than creating my own server to deal with the authorisation ?

I am using Ember as the front end with Ember simple auth and hopefully using the linked library for the backend.